1. Field of the Invention
The present invention relates generally to magnetic recording and reproduction apparatus and magnetic tape for use in such apparatus and, more particularly, to a magnetic recording and reproduction apparatus employed as a storage apparatus requiring a faster recording function and a faster search and reproduction function, and a magnetic tape employed in such apparatus.
2. Description of the Background Art
For recording and reproducing digital data at a high speed, a hard disk, a rewritable type optical disk or the like is principally employed as a recording medium at present.
The hard disk is a magnetic disk using a disk-like aluminum substrate or glass substrate. Recording tracks of the magnetic disk are formed in a concentric form on the disk. Recording and reproduction of information for the hard disk is made by rotating the hard disk at a high speed, thereby to make magnetic heads trace on the recording tracks on the hard disk at a high speed. The rewritable type optical disk is an optical disk capable of recording and erasing data many times on the same track or the same sector. Recording tracks of the optical disk are also formed in a concentric form or spiral form on the optical disk. Recording and reproduction of information for the optical disk is made by irradiating the recording tracks of the optical disk with a laser beam while rotating the optical disk at a high speed. Optical properties of the recording layer or the rewritable type optical disk reversibly vary by irradiation with a laser beam. This enables rewriting of the information.
In general, a spindle motor is used for rotating such a disk-like recording medium as a hard disk or optical disk.
There are two types of recording and reproduction apparatus capable of recording and reproducing digital data: the one employs such a disk-like recording medium as represented by the hard disk or optical disk, and the other employs a tape-like recording medium. The recording and reproduction apparatus employing such a tape-like recording medium includes a recording and reproduction apparatus of an R-DAT system (Rotary Head Digital Audio Tape Recorder) in which data is recorded and reproduced on a magnetic tape by using a rotary head.
FIG. 6 is a diagram showing a track pattern on magnetic recording by the R-DAT system. FIG. 7 is a diagram showing the state of a rotary drum system portion in the R-DAT type recording and reproduction apparatus. Referring to FIG. 7, magnetic heads (not shown) for recording and reproducing data for a magnetic tape 3 are attached on outer peripheries of a drum 6. Drum 6 is rotated at a high speed by a motor 7. Drum 6 is secured with an inclination of a definite angle (e.g., 7.degree. 50') relative to magnetic tape 3. Magnetic tape 3 is moved in its elongated direction. With drum 6 fixed with an inclination of a definite angle to magnetic tape 3, rotation of drum 6 causes the magnetic heads attached onto drum 6 to trace on magnetic tape 3 obliquely to the moving direction of magnetic tape 3. Thus, as shown in FIG. 6, parallel recording tracks 4 inclined at a definite angle relative to the moving direction of magnetic tape 3 are formed on magnetic tape 3. In general, two magnetic heads are mounted at respective positions which are 180.degree. apart from each other on outer peripheries of drum 6. The respective two magnetic heads have different azimuths in order to prevent occurrence of a phenomenon (cross talk) in which those magnetic heads pick up not only a signal of a recording track which is inherently to be traced but also a signal of a recording track adjacent to that recording track. Thus, the two adjacent ones of recording tracks 4 formed on magnetic tape 3 are traced by the respective magnetic heads having different azimuths.
For a recording and reproduction apparatus for recording and reproducing an audio signal as a digital signal, there is a tape recorder of an S-DAT system (Stationary Head Digital Audio Tape Recorder) in which information is recorded and reproduced on a magnetic tape by using a fixed multi track head not using a rotary head. FIG. 8 is a diagram showing a track pattern on the magnetic tape by the S-DAT system. FIG. 9 is a diagram showing a fixed multi track head portion in the tape recorder of the S-DAT system. Referring to FIG. 9, a multi track head 8 is fixed at a position facing a recording surface of a magnetic tape 3 (corresponding to the back side of the sheet of FIG. 9). Magnetic tape 3 moves in its elongated direction.
Multi track head 8 includes a plurality of magnetic heads H1, H2, . . . , Hn (n is a natural number not lower than 2) arranged in parallel. The plurality of magnetic heads Hl-Hn are in general thin-film heads and integrated together. The thin-film heads are magnetic heads produced by a thin-film forming technology such as sputtering, evaporation, electrodeposition or the like and an IC process technology. Each of the magnetic heads has a magnetic core and a coil wound around the magnetic core. The thin-film heads are integrally formed including smaller and planar magnetic cores and coils in the same process as that of semiconductor devices. Heads Hl-Hn are arranged with a definite distance apart from each other. Thus, if magnetic tape 3 moves, then as shown in FIG. 8, recording tracks 1-1 to 1-n are formed with a definite spacing from each other on magnetic tape 3, corresponding to magnetic heads Hl to Hn. Portions 2 between any recording tracks 1-1 to 1-n, on which no information is recorded are called guards. A digital audio signal is recorded on each of recording tracks 1-1 to 1-n. A series of serial digital signals are recorded individually on recording tracks 1-1 to 1-n.
According to the S-DAT system, as described above, information is recorded in parallel on magnetic tape 3 separately for a plurality of channels. With multi track head 8 formed of the thin-film heads, each of heads Hl-Hn can be reduced in scale. This entails reductions in the width of each of recording tracks 1-l to 1-n and the width of each of guards 2. Thus, the number of channels in a single magnetic tape, i.e., the number of recording tracks formed in parallel to the moving direction of magnetic tape 3 can be increased with the reduction in the scale of heads Hl-Hn. For example, a tape recorder of the S-DAT system in which recording tracks of 20 channels or so are formed on a magnetic tape having a width of 3.81 mm is implemented for practical use at present.
In the case where each of sampled audio signal voltages is converted to 16-bit digital data when an analog audio signal is digitized in recording onto a magnetic tape, for example, if the number of channels of the magnetic tape is 16, then a digital audio signal is recorded on the magnetic tape so the data of respective ones of 16 bits may correspond to respective ones of recording tracks of the magnetic tape in a one-to-one correspondence. More specifically, digital signals indicating the sampled audio signal voltages are allotted to 16 channels for respective bits and recorded time-sequentially. Accordingly, the digital audio signal is recorded in parallel to the moving direction of the magnetic tape in real time.
As described above, the recording and reproduction apparatus using the disk as a recording medium has been mainly applied as a conventional recording and reproduction apparatus requiring a faster recording and a faster search and reproduction. This results from the following reasons.
When a disk is used as a recording medium, recording tracks are formed in the form of a concentric circle about the center of the disk, on a recording surface of the disk. Recording and reproduction of information for the disk is carried out, with a head supporter called an "arm" which has a head mounted on its tip end being moved in a radial direction of the disk. Thus, in order to search for necessary information from the disk, it is necessary to move the arm in the radial direction of the disk to find out recording/reproduction tracks on which the necessary information is recorded/reproduced. Thus, since the movement of the arm for searching for the information is not larger than the radius of the disk, the information is searched for at a relatively high speed.
On the other hand, when a magnetic tape is used as a recording medium, recording tracks are formed in parallel to the moving direction of the magnetic tape by a fixed head in accordance with the S-DAT system. Information is then recorded time-sequentially on the recording tracks. Thus, in order to search for necessary information from the magnetic tape, it is necessary to fast forward or rewind the magnetic tape to move a portion of the recording tracks, on which the necessary information is recorded, to the position of the fixed head. Therefore, a maximum value of the forwarding or the rewinding of the magnetic tape required for the search for the information is equal to the total length of the magnetic tape. It is thus relatively difficult to search for the necessary information from the magnetic tape at a high speed. For the same reason, it is more advantageous to use the disk as a recording medium than the magnetic tape in recording information at a desired position on the recording tracks at a high speed.
As described above, if the disk is employed as a recording medium, the head can be moved to an arbitrary recording track, skipping any recording tracks interposed therebetween only moving the arm in the range of a short distance, thereby enabling a faster recording and a faster search and reproduction.
There is also an R-DAT system for the magnetic tape recording system. In the R-DAT system, however, a plurality of recording tracks are formed obliquely to the moving direction of the magnetic tape. Thus, if a single head is mounted on a rotating drum, a second recording track does not start to be traced soon after a first one recording track is traced. More specifically, a definite time period corresponding to rotating speed of the drum is provided between time that the head reaches a tracing end position of the first recording track and time that the head reaches a tracing start position of the second recording track. Thus, information recorded on each of the recording tracks is liable to be discontinuous at junctions of the recording tracks. In order to decrease such a phenomenon, a plurality of heads are mounted on the drum, thereby reducing the period between the time that one recording track is traced and the time that the next recording track starts to be traced. However, also in the R-DAT system, information is recorded time-sequentially in accordance with the moving direction of the magnetic tape, and hence it is difficult to realize a faster recording and a faster search and reproduction.
For the above reasons, a disk is often employed as a recording medium in a recording and reproduction apparatus used for information processing such as a computer. Under such circumstances, a still larger recording capacity and a still faster access function have recently been required for a recording and reproduction apparatus for use in equipment having an information processing function.
In order to increase a storage capacity of the disk, it is necessary to increase a radius of the disk to increase the number of recording tracks. However, it is impossible for practical use to infinitely increase the radius of the disk. Thus, there is inevitably a limitation in the increase in the recording capacity of the recording and reproduction apparatus using the disk as a recording medium. On the other hand, in order to increase the capacity of the recording and reproduction apparatus using a magnetic tape as a recording medium, it is necessary to increase the length of the magnetic tape. Necessary alteration for the recording and reproduction apparatus in accordance with a change in the length of the magnetic tape is made with only respect to the size of a cartridge for use to lap the magnetic tape. Thus, the recording capacity of the recording and reproduction apparatus using the magnetic tape as a recording medium can be increased relatively easily without being limited for practical use as compared to the recording capacity of the recording and reproduction apparatus using the disk as a recording medium. That is, with regard to an improvement in recording capacity, it is more advantageous to use the magnetic tape as a recording medium.
As equipment having the information processing function becomes smaller and more portable, a lighter and smaller recording and reproduction apparatus is required for use in such equipment. As mentioned before, when a disk is used as a recording medium, a spindle motor for rotating the disk is necessary. In addition, the recording and reproduction apparatus of the R-DAT system using a rotary head requires a motor for rotating a drum on which a head is mounted (motor 7 of FIG. 7). Thus, the recording and reproduction apparatus using the disk as a recording medium cannot be designed in such a thin form that the height of the apparatus is lower than the height of the spindle motor. Similarly, with reference to FIG. 7, the recording and reproduction apparatus of the R-DAT system cannot be made thinner than the sum of L1 of the height of drum 6 and the height of motor 7 for rotating drum 6. That is, there is inevitably a limitation in reduction in the scale of the recording and reproduction apparatus. On the other hand, the recording and reproduction apparatus of the S-DAT system using a fixed head does not require such a motor as described above and hence, with reference to FIG. 9, the apparatus can be designed as thin as approximately the width L2 of head 8. Therefore, with regard to the reduction in the scale of the apparatus, the recording and reproduction apparatus of the S-DAT system is more advantageous than the apparatus of the R-DAT system. However, the recording and reproduction apparatus using the magnetic tape as a recording medium is disadvantageous in respect of the faster recording and the faster search and reproduction as mentioned above.